PB1873: OUTCOMES OF PATIENTS WITH POSSIBLE GERMLINE AND SOMATIC CEBPA-MUTATED ACUTE MYELOID LEUKEMIA BASED ON VARIANT ALLELE FREQUENCY (VAF): A SINGLE-CENTER RETROSPECTIVE STUDY
Authors: Sheraz Bashir, Chrishthuka Kangatharan, Victor Ling, Michelle Richardson, Seoksan Teh, Jayne Chappells, Debo Ademokun, Andrew Hodson, Mahesh Prahladan
Journal: HemaSphere (2023)

Topic: 4. Acute myeloid leukemia - Clinical Background: The transcription factor CCAAT/enhancer binding protein-α (CEBPA) is found in patients with acute myeloid leukemia (AML) and are associated with a favourable outcome. However, the distinction between germline and somatic CEBPA mutations is clinically significant, as patients with germline CEBPA mutations have implications in therapeutic interventions and in predictive assessment in siblings and offspring. Aims: In this retrospective study, we aimed to identify patients with CEBPA mutations and distinguish between germline and somatic mutations based on the Variant Allele Frequency (VAF) of using Sanger’s next generation sequencing (NGS) and whole genome sequencing (WGS). We also sought to evaluate the clinical outcomes of these patients and explore potential differences in disease progression and treatment response. Additionally, we aimed to determine whether the presence of other gene mutations in CEBPA-mutated AML patients affects their clinical outcomes. Methods: We retrospectively analysed medical records of 51 AML patients diagnosed and treated at our hospital between January 2018 and December 2022. Genomic DNA from blood or bone marrow was extracted, and CEBPA mutations were identified using using Sanger’s next generation sequencing (NGS) and whole genome sequencing (WGS). The NGS technique allowed identification of mutations and their frequency which prompted for additional investigation to exclude germline variants. However, tissue or saliva samples were not analysed to confirm germline mutation variants. Potential germline mutations were only considered for patients with a high variant allele frequency of more than 50%. We collected data on patient demographics, diagnosis, treatment regimens, and clinical outcomes. The NGS technique used in this study involved utilizing a targeted TWIST panel to capture exons of 75 Haem-Onc genes. The Illumina NovaSeq was used for sequencing, and GATK and pindel were used for variant calling with a limit of detection of 5% variant allele frequency. The assay does not exclude the presence of variants outside the targeted regions or large insertions/deletions, gene copy number alterations, or gene rearrangements. Results: Our analysis revealed a CEBPA mutation frequency of 11.8% in our AML patient cohort, with 5.9% likely germline and 5.9% likely somatic mutations. Of the 6 patients with CEBPA mutations, 3 patients (50%) had other gene mutations in addition to their CEBPA mutations. Among the 3 patients with likely germline mutations, all achieved complete remission after standard induction chemotherapy, and their median overall survival (OS) was not reached at the time of data analysis. For the 3 patients with likely somatic mutations, 1 achieved complete remission and is alive at the time of analysis, while the other 2 died of progressive disease. The median OS for the 3 patients with likely somatic mutations was 8 months. Patients with other gene mutations had lower OS compared to those without other gene mutations. Summary/Conclusion: Our study suggests the incidence of CEBPA mutations in our AML patient cohort reflected the incidence seen in the literature. Germline CEBPA mutations were associated with a favourable prognosis, and their identification has important therapeutic and prognostic implications. Our findings support the importance of follow up tissue sample for germline confirmation in patients with AML with CEBPA mutations.The use of NGS and WGS with VAF help to predict the germline and somatic variations of CEBPA mutations in AML patients, enabling better treatment planning and disease management. Keywords: Genomics, Somatic mutation, Mutation analysis, Acute myeloid leukemia